Traditionally, livestock have been contained by gates and the like which generally must be manually operated and are difficult to maneuver through, especially if an unassisted driver must move heavy equipment through a gate in an enclosure used to confine a large group of animals. The "cattle grid", sometimes called a "Texas Gate", was invented to permit unattended free access to an enclosure while confining animals. The conventional cattle grid comprises an open grid construction which is installed over an open-topped, generally rectangular pit in the ground. The pit, which is commonly about a half meter deep, is excavated in a path or roadway in place of a traditional gate. The spaces in the open grid construction are preferably wider than the length of the hooves of the animals to be confined. Animals are therefore unable or afraid to maneuver their way across the barrier, while vehicles and people are readily capable of crossing the grid over the top of the pit.
Although the conventional cattle grid provides distinct advantages over gates and the like, there are several drawbacks which render it undesirable in certain situations. First, a large pit must be excavated, the walls retained, the pit drained and the excavated earth disposed of. The construction of a cattle grid is therefore an expensive and time-consuming operation. In addition, once the structure is built, it is permanent in nature. In order to remove it, the open grid construction must be removed, the pit refilled and the surface of the road or path repaired. Access to the area is, of course, impossible during either the construction or removal of traditional cattle grid.
In order to overcome the disadvantages of the traditional cattle grid, pitless cattle grid structures were invented to contain livestock while permitting ready access to an area by vehicular and pedestrian traffic. Two known alternatives are described in U.S. Pat. No. 4,708,515 entitled STOCK BARRIER which issued to Davies on Nov. 24, 1987 and French Patent Application Number 2,573,621 which was filed by Grospiron on Nov. 29, 1984.
The STOCK BARRIER to Davies describes a cattle grid which comprises a plurality of rigid metal panels of open grid construction that are arranged to lie in a normal operational position at an angle to the ground to thus form a pair of back-to-back ramps across which stock will not cross but which can be flattened to the ground against a resilient return force when a vehicle is driven across. Although this apparatus represents an improvement in some respects over the traditional cattle grid, it has several disadvantages which detract from its desirability. First, the structure is not portable. It requires a pair of opposed sturdy support posts which must be set in concrete or the like to support the structure, so it is relatively expensive to install. Second, in order to permit the opposed side edges of the open metal work panels to flatten against the ground when a vehicle embarks the stock barrier, a very firm level surface must be provided. This means that the cattle grid must be installed over an asphalt or concrete surface and runners must be installed under certain portions of the grid to provide for its reliable operation. Finally, because of the construction of the cattle grid, it is potentially hazardous for vehicles with a very long wheelbase as the V-shaped grid could be pulled upward by the return springs when the front wheels leave the grid, causing damage to the undercarriage of the vehicle due to contact between the undercarriage and the top of the V-shaped grid.
French Application Number 2,573,621 describes a barrier for livestock with cloven hooves. The barrier comprises a rectangular array of Y-shaped sculpted plates which are interlocked to form a planar grid having equally spaced Y-shaped projections which prohibit such animals from crossing the array in one direction due to pain inflicted in their distal hoof ligament by the projections. The advantage of the structure is that it theoretically permits the one-way passage of animals across the barrier. It also permits vehicular traffic over the barrier in either direction. The disadvantage of the structure is that the interlocking plates are preferably set in a bed of wet concrete. The barrier is, therefore, a permanent structure which requires a relatively lengthy and expensive installation. Besides, it only prevents the circulation of animals with cloven hooves and then in only one direction. It further appears to be an expensive alternative in that each element of the array must be precisely manufactured to relatively exacting tolerances.
Certain industries such as the oil exploration industry, for example, often require access to fenced cattle ranges for an indefinite term. In order to facilitate access to a fenced area while minimizing the risk of having cattle escape from the area, cattle grids of the traditional pit type are generally installed. Such installations contribute to operating expenses of exploration and generally slow the progress of opening new areas. There, therefore, exists a need for a reusable, portable livestock barrier which is quickly and easily installed with a minimum of time and effort.
It is an object of the present invention to overcome the problems of known prior art cattle grids.
It is a further object to present invention to provide a livestock barrier which is readily portable.
It is yet a further object of present invention to provide a livestock barrier which does not require special support surface preparation for its installation and use.